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When I added winter tires to my order it showed up under "View Design" in few hours (was told to expect 2 days). About 18 days after the change was requested I got an email telling me the change had been made and another email telling me that a new document had been uploaded to "My Tesla" (the "Delivery Configuration").

Adding tires might be faster because there's really nothing for them to do during production. It's not clear if they include the tires in the vehicle coming from the factory or if they just ship wheels/tires to the SC and add them to the car there. But either way it shouldn't change much. So they can probably just casually say yes that's no problem to the change I made.

If you're adding what I think you're adding then that probably takes more effort in adjusting the production for the car and probably requires more approvals.

When I made a change (by phone) they said it could take up to a week but it was reflected online after about two days. It may just be at the mercy of the person making the change manually and when they get around to it. If it's been more than a week I'd probably email them to ask when to expect to see the change online. If nothing else, it'll be a gentle reminder for them to make the change if they haven't already.